A feature only fires for some sessions — how do you power and read it? — Pinterest Product Data Science Data Scientist Interview

A feature only fires for some sessions — how do you power and read it?

Experiment designHard

Problem. You're testing a Homefeed feature that only activates on a slice of sessions (say, sessions where a certain module can render — maybe 15% of sessions). On an all-users read the save lift looks tiny and "not significant." How do you design and read this correctly?

Before you reveal: say your answer out loud, as if you were in the real interview — get your reasoning across clearly first. There is no single correct answer: reading what the interviewer is really after and defending your own thinking is what makes an answer strong.